The continued objectives of this project are to define the biochemical mechanisms controlling the synthesis, storage, release, action, and termination of action of neurotransmitters and to determine how genetic factors, environmental stimuli, or drugs influence these control mechanisms. During the last year the alterations in release of catecholamines from the adrenal medulla and sympathetic nerves into plasma in genetic hypertension, after various drugs, and during stress have been studied in intact rats. In vitro the influence of presynaptic receptors on release has been examined in cultured sympathetic ganglia. BIBLIOGRAPHIC REFERENCES: Grobecker, H., Roizen, M.F., and Kopin, I.J.: Effect of tyramine and guanethidine on dopamine-beta-hydroxylase activity and norepinephrine concentrations in vesicular fraction of the heart and plasma of rats. Life Sci. 20: 1009-1016, 1977. Kopin, I.J.: Noradrenergic Neurotransmission. In Lipton, M.A., DiMascio, A., and William, K.F. (Eds.): Psychopharmacology: A Generation of Progress. New York, Raven Press, 1977. (In Press.)